This paper proposes a recognition algorithm based on signal-to-noise ratio estimation for the identification of non constant modulus signals in asymmetric paired carrier multiple access (APCMA) in satellite communication signals. Firstly, the algorithm performs power spectrum estimation on the received signal to calculate the observed signal-to-noise ratio; secondly, by calculating the effective signal-to-noise ratio through high-order moment calculation and combining it with constellation moment algorithm, the problem of large errors in the effective signal-to-noise ratio of non constant modulus signals in high-order moment calculation has been solved; finally, based on the characteristic that the observed signal-to-noise ratio of the mixed signal is higher than the effective signal-to-noise ratio, a feature parameter M was designed to achieve the recognition of non constant modulus APCMA signals. The experimental results show that the proposed algorithm achieves a recognition rate of nearly 100% for non constant modulus APCMA signals when the signal-to-noise ratio of weak signals is greater than 0 dB.